Background: Determinations of serum levels of prostate specific antigen (PSA) are widely used for the detection of prostate cancer, but have not demonstrated sufficient sensitivity and specificity to be useful in urological practice. In order to enhance the diagnostic value of serum PSA, we studied the distribution of serum PSA levels by age in urological patients without clinical evidence of prostate cancer and determined clinical PSA reference values by age decades.
Methods: The study included a total of 590 male patients aged 40 to 89 years who visited our urological clinic complaining of voiding symptoms from January 1991 to October 1994, but had no clinically evident prostate cancer. We defined patients to be without clinical evidence of prostate cancer if they had negative test results in digital rectal examination, ultrasonography, and serum PSA assay, or had positive test results in one or more of these tests but had a nonmalignant prostate biopsy. Serum PSA levels were measured by E-Test Tosoh II (AIA-PACK PA, normal range; 0 to 5.3 ng/ml). The patients were grouped by age decades and serum PSA values were given as percentiles.
Results: Analyzed by Pearson's correlation coefficient, serum PSA levels were correlated significantly with patient age (r = 0.24, p < 0.001). Prostatic volume was correlated weakly but significantly with patient age (r = 0.12, p = 0.005), and PSA density was also correlated significantly with patient age (r = 0.20, p < 0.001). Thus, serum PSA levels were demonstrated to increase with advancing patient age. Factors other than benign prostatic hypertrophy were also suggested to explain the increase in serum PSA levels in older patients. With the 95th percentile for serum PSA as the upper limit, the clinical PSA reference values by age decades were determined to be 2.6 ng/ml for patients aged 40 to 49 years, 5.0 ng/ml for 50 to 59 years, 7.5 ng/ml for 60 to 69 years, 10.1 ng/ml for 70 to 79 years, and 12.4 ng/ml for 80 to 89 years.
Conclusion: We found a significant increase in serum PSA levels with advancing patient age. Thus, it is appropriate to have serum PSA reference values by age decades. Prospective clinical trials are necessary to define the usefulness of the PSA reference values by patient age in urological practice.